How doctors think

Dr. Jerome Groopman, M.D. has written How Doctors Think (Mariner Books) It has some helpful information for lawyers. I was interested in the following description of how doctors are trained to make a diagnosis. He says:

"Medical students are taught that the evaluation of a patient should proceed in a discrete, linear way: you first take the patient’s history, then perform a physical examination, order tests, and analyze the results. Only after all the data are compiled should your formulate hypotheses about what might be wrong. These hypotheses should be windowed by assigning statistical probabilities, based on existing databases, to each symptom, physical abnormality and laboratory test; then you calculate the likely diagnosis. This is Bayesian analysis, a method of decision making favored by those who construct algorithms and strictly adhere to evidence based practice. But, in fact, few, if any physicians, work with this mathematical paradigm. The physical examination begins with the first visual impression in the waiting room and with the tactile feedback gained by shaking a person’s hand. Hypotheses about the diagnosis come to a doctor’s mind even before a word of the medical history is spoken."

The author quotes Dr. Francis Weld Peabody of Harvard Medical School who said, during a lecture in 1925:

‘The secret of the care of the patient is in caring for the patient.’"

I often have asked experts during cross examination about Occam’s Razor – the principle of logic which roughly says that where there are multiple possible explanations, the simplest is the most likely to be correct. Groopman acknowledges this is the approach taught medical students. He notes, however, that this approach can lead to a wrong diagnosis. He says:

"Physicians should caution themselves to be not so ready to match a patient’s symptoms and clinical findings against the their mental templates or clinical prototypes…’common things are common’ is another cliché’ that was drilled into me during my training. Another echoing maxim on rounds: ‘when you hear hoof beats, think about horses, not zebras’"

In discussing the fact that different physicians can reach different conclusions on the same data he describes a study where a group of experts looked at the same 100 EKG’s. The experts agreed that50 showed a myocardial infarction, 25 were normal and 25 showed various abnormalities. These same EKG’s were then given toother cardiologists to test their diagnostic skills. Their diagnosis resulted inwidely divergent conclusions. So that if you were the patient andto Dr. Athere was a 20% chance he would miss the infarct. If you did not have an infarct and wen to Dr. B, there was a 26% chance he would say you had one when you didn’t. The same kind of conflicting conclusions by the doctors looking at the same report involved pathologists. In that study 1001 specimens obtained from biopsies of the cervix were read by thirteen pathologists. After a time delay the same pathologistwere given the same slides to read a second time. The result was that the conclusionsreached the first time the read the slide was in conflict with the same slide when they read it later.

We all know the influence of the pharmaceutical industry on medicine. In their effort to market their products they have managed to corrupt research and influence physician prescriptions. I found it interesting that the author interviewed Douglas Watson who had been a pharmaceutical executive for thirty three years and was CEO of Norvartis Corporation. Watson said that their marketing studies showed that most physicians routinely prescribed only around two dozen drugs and that the majority of these drugs were adopted for use by them during their medical training or shortly thereafter. This explains the marketing efforts made by pharmaceutical companies in medical training. Once the physician begins using the product he or she is likely to continue using it throughout their practice. This is consistent with the tobacco industry that fought over marketing their brand to children because their marketing studies revealed that the brand they used as adolescents was likely to be the brand they used for life.